1. Field of the Invention
The present invention relates to a so-called retractable barrel type camera which is arranged such that a lens barrel of zoom system can be retracted into a camera body, and more particularly to a control in retracting the lens barrel.
2. Related Background Art
A recent demand is to reduce the outer dimensions of camera, particularly of compact camera. Especially, an important subject is to miniaturize a lens barrel as much as possible. To miniaturize the lens barrel, a recent trend in camera having the two lens group zoom system is to replace a mechanical cam system with a mechanism for driving the front lens group and the rear lens group by separate motors.
An example of the two lens group zoom system is one as shown in FIGS. 1A and 1B. A lens barrel 4 of the zoom system 2 is composed of a stationary barrel 6 forming a part of camera body, an intermediate barrel 8 telescopically stored in the stationary barrel 6, and a movable barrel 10 telescopically stored in the intermediate barrel 8.
A front lens group (FLG) 22 which consists of one or more lenses is fixed in a front end portion of the moving barrel 10 and is arranged to be driven by a direct current (DC) motor (not shown in FIGS. 1A and 1B) to move backward and forward together with the moving barrel 10.
Also, a rear lens group (RLG) 28 which consists of one or more lenses is arranged behind the front lens group 22 (on the camera body side) in the moving barrel 10 so as to be movable backward and forward. The rear lens group 28 is driven backward and forward by a stepping motor (not shown in FIGS. 1A and 1B).
FIG. 1A indicates an extreme telephoto state in which the focal length is the longest and FIG. 1B indicates an extreme wide-angle state in which the focal length is the shortest.
Such a zoom system 2 is generally so arranged that with no occasion to shoot, the moving barrel 10 and the intermediate barrel 8 are further retracted from the extreme wide-angle state as shown in FIG. 1B into the stationary barrel 6 to store the entire lens barrel 4 at a retracted position in the camera body. However, if the lens barrel 4 were moved to the retracted position with the rear lens group 28 being kept at the position of extreme wide-angle state, the rear lens group 28 would come into contact with a film F, which could damage the film F.
Thus, the conventional camera is so arranged that in retracting the lens barrel 4 into the camera body, the rear lens group 28 is first moved to a predetermined standby position where it is located closest to the front lens group 22 and thereafter the lens barrel is retracted.
However, if the rear lens group 28 fails to be located at the predetermined standby position because of some cause, the conventional two lens group zoom system as described above has a possibility that the rear lens group 28 would contact the film F when the lens barrel 2 is retracted into the camera body in that state.
Especially, in case of a motor for driving the rear lens group 28 being a stepping motor, the above point must be fully taken care of. The stepping motor could cause a step-out state in which it is not normally driven with application of pulse, if a drive voltage thereof is lowered. A position of the rear lens group is normally obtained from a cumulative number of pulses applied to the stepping motor. Therefore, once the step-out state occurs, an actual position of the rear lens group becomes lost, which could cause contact between the rear lens group and the film.
Consequently, a need exists for a way to prevent contact between the rear lens group and the film in retracting the lens barrel.